Diseases & Conditions


Year-Round Allergies (Perennial Allergies)

Year-round (perennial) allergies result from exposure to airborne substances (such as house dust) that are present throughout the year. The nose is congested, itchy, and sometimes runny, and the mouth and throat are itchy The symptoms and activities that trigger the allergy usually suggest the diagnosis. Avoiding the allergen is best, but drugs, such as antihistamines, can help relieve symptoms.

Perennial allergies may occur at any time of year—unrelated to the season—or may last year-round. Perennial allergies are often a reaction to house dust. House dust may contain mold and fungal spores, fibers of fabric, animal dander, dust mites, and bits of insects. Substances in and on cockroaches are often the cause of allergic symptoms. These substances are present in houses year-round but may cause more severe symptoms during the cold months when more time is spent indoors.

Usually, perennial allergies cause nasal symptoms (allergic rhinitis) but not eye symptoms (allergic conjunctivitis). However, allergic conjunctivitis can result when certain substances are purposely or inadvertently placed in the eyes. These substances include drugs used to treat eye disorders, cosmetics such as eyeliner and face powder, and hair dye. The cleaning solutions for contact lenses can cause a chemical allergic reaction.

Symptoms and Diagnosis

The most obvious symptom is a chronically stuffy nose. The nose runs, producing a clear watery discharge. The nose, roof of the mouth, and back of the throat may itch. Itching may start gradually or abruptly. Sneezing is common.

The eustachian tube, which connects the middle ear and the back of the nose, may become swollen. As a result, hearing can be impaired, especially in children. Children may also develop chronic ear infections. Some people have recurring sinus infections (chronic sinusitis) and growths inside the nose (nasal polyps). When affected, the eyes water and itch. The whites of the eyes may become red, and the eyelids may become red and swollen.

Many people who have a perennial allergy also have asthma, possibly caused by the same allergens that contribute to the allergic rhinitis and allergic conjunctivitis.

Diagnosis is based on symptoms plus the circumstances in which they occur—that is, in response to certain activities, such as petting a cat.

Did You Know...

Cockroaches are often to blame for allergies.


Avoiding the allergen, if possible, is recommended, thus preventing the development of symptoms.

If people are allergic to house dust, some changes in the environment can prevent or lessen symptoms: Removing items that collect dust, such as knickknacks, magazines, and books Replacing upholstered furniture or vacuuming it frequently Replacing draperies and shades with blinds Removing carpets or replacing them with throw rugs Covering mattresses and pillows with finely woven fabrics that cannot be penetrated by dust mites and allergen particles Using synthetic-fiber pillows Frequently dusting and wet-mopping rooms Using air conditioners and dehumidifiers to reduce the high indoor humidity that encourages the breeding of dust mites Installing high-efficiency air filters


Drug treatment is similar to that for seasonal allergies. It includes antihistamines, nasal decongestants, and corticosteroid nasal sprays.

For people with chronic sinusitis and nasal polyps, surgery is sometimes needed to improve sinus drainage and remove infected material or to remove the polyps. Before and after surgery, regularly flushing out the sinuses with a warm water and salt (saline) solution may be helpful. This technique is called sinus irrigation.

Last full review/revision September 2008 by Peter J. Delves, PhD

Source: The Merck Manual Home Edition